Anglo said:
Hi Steve, yes, the response was in reply to your post. Nothing derogatory was implied, since all of us have different working methods, and I respect the "all paths to the mountain" approach. I use subjective tuning myself, but without hard, repeatable data I find it very hard to get to the root of why a given coloration is there, and how to remove or minimize it. Fiddling around with equalization just leads me around in circles and leads to annoyance and frustration.
With unsmoothed FR, CSD, and impulse measurements, I can track down what aspect of the speaker is screwing up and is responsible for the coloration. This has to be done one driver at a time, with and without the crossover network, in the intended baffle, and measuring both nearfield and 2+ meters away, and at a number of different emission angles.
If a narrowband resonance (as seen in the CSD waterfall or time response) is also narrow in directivity, that spells trouble. Diffraction (and resulting standing-wave) off a sharp boundary is a very possible cause - a little quick math (sound travels 343 meters/second) will show if the hard edge is about the right distance from the diaphragm. Temporary treatment methods on the edge may then show up in the CSD, but they may not, depending on your CSD resolution (be sure to absorb the floor-bounce at 3 mSec with 2 feet of pillows, and use a low-diffraction mike stand, as shown below).
I am always on the lookout for narrowband artifacts - these indicate diffraction, diaphragm breakup, or a malign combination of the two. If the artifact is highly directional, diffraction is probably involved - that is the hallmark of diffraction. (Again, these are single-driver measurements - crossover and polar-pattern integration is a completely separate issue.)
If the artifact is non-directional, then I suspect a more general problem like diaphragm breakup or resonance. With a horn system and phase-plug, some very complex interactions are possible, with several problems all happening at once. Note that many of these problems do not respond to equalization, since they are time and spatial-domain errors, and EQ will only make them worse, not better.
Thus, the desire to mix-and-match several compression driver and horn combinations, to better understand the contribution of each. I expect I'll be trying stunts like putting a wool sock in the throat of the horn to see what impact that has on the time response.
Jmmlc said:
Jean-Michel, I want to thank you for joining the thread - as the designer of the Le Cleac'h profile, I give particular weight to your remarks. I was curious myself about the air-load reactivity of the larger vs smaller horn, and the possibility of "wasting" some of the potential midrange bandwidth of the 1.4" format 288 compression driver due to the 550 Hz horn being just too small to take full advantage of it. (If that's true, perhaps the best application of the 550 Hz horn is to mate with 1" format compression drivers.)
I've been curious why the 340 and 550 have the cutoff frequencies they do, since the 340 is just about twice as large (in every dimension) as the 550. At first glance, it would seem like either the 340 is really a 275 Hz horn, or the 550 is really a 680 Hz horn.
Martin Seddon tells me that with a 1-3/8" (35mm) throat and mounting plate (to match an Altec 288), the AH-340 is 349mm long, has a 600mm overall diameter, and is 500mm across when measuring the portion of the horn-mouth that is at a 90-degree angle to the central axis. With the same size mounting plate, the AH-550 is 168mm long, and has a 300mm overall diameter (and I'm guessing is 250mm across where the flare reaches 90 degrees).
I'm curious what the "T" function of the equation represents - is that the net overall flare-rate of the entire horn, or a ratio that represents possible shapes with either more or less curvature than a Tractrix? Does this control the sharpness of the acoustic highpass filter?
I plan to use an elliptic highpass function with the notch tuned to the Fs (in the horn) of the 288 driver, in order to control out-of-band excursion as efficiently as possible, but without the time-domain penalties of a high-slope 24 dB/oct crossover. This filter topology should allow freedom from having to "tune" the horn cutoff and rear-chamber volume in order to form an acoustic highpass filter - this was necessary when the Altec 12 dB/oct crossover was all that was available, but today we can use more sophisticated filter functions to control excursion and optimize time-domain response.
I'll also looking at the filter function you have described on your web-page - whatever gives the best performance for the application (which in this case is mating with a 12" woofer, either Altec 414, Tone Tubby, or 18Sound). If the 340 delivers an extra half or two-thirds of an octave compared to the 550, that's a considerable advantage in terms of matching with the 12" woofer, regardless of crossover topology.
Attachments
Jmmlc said:
Are you saying you don't use your horns below reactance? Seems to me most people that use the Azura horns do.
The directivity can be a real problem. I have followed this thread for a while and if you read into what Lynn expects (correct me if I'm wrong Lynn) he wants to have controlled wide dispersion and wants to mate the compression driver to a ribbon of wide dispersion. With the big horn he'll be hanging the ribbon some 16 or so inches from the throat and wanting to time align it. IME it will be a challenge he wishes he didn't take. The big horn will be narrow dispersion at it's top end while the ribbon is at it's widest... there is also going to be reflections, and distance between the two.
Well, part of the reason I want to get rid of the horn above 7~10 kHz is that's where compression drivers and horns start to get in real trouble - for many reasons: diaphragm breakup, spurious emission from the surround, rapidly increasing harmonic and IM distortion, phase plug diffraction, beamwidth narrowing in the horn, increasing severity of HOM's with increasing frequency, a whole host of problems that are not trivial to solve.
It's not entirely a coincidence that the important compression-driver patents (Wente, et al) date back to the days of optical sound-film, with its 8 kHz bandwidth limitation. It wasn't until Dolby and THX started requiring flat response to 15 kHz and beyond that JBL and Altec were forced to re-visit the compromises of the 1945 technology of the Altec 288 and JBL 375.
One of the unusual things about the 7~10 kHz region is that narrow notches in the response are not very audible. Normally, a crossover with the drivers several wavelengths apart is a bad idea due to severe lobing in the plane of drivers. It certainly is tedious to measure, since microphone movements of a few inches cause ripples in the response. I've done supertweeters before, and this particular kind of multi-wavelength crossover is as close to inaudible as any crossover can be. (I still expect some weirdnesses due to the horizontally-wide but vertically-narrow dispersion of the ribbons and what the AH-340 or AH-550 looks like at 7 kHz (2" wavelength). I also expect the 35mm throat size will begin to dominate the pattern of either horn - another reason to cross over to a direct-radiator.)
That is very different from crossovers in the 300 Hz to 5 kHz region, where any errors are immediately audible as a lack of integration and weird position-dependent colorations. Even the famous Lowther is afflicted with a mechanical crossover in the 3~5 kHz region, and this transition to the whizzer-cone is plenty audible and measurable. Crossovers at lower frequencies tend to merge with room colorations due to the very long wavelengths (in practical terms, they can cause unpredictable room colorations that aren't obvious from near-field measurements).
In this design, the really critical crossover is the transition between the 12" direct-radiators and the horn driver. The highpass filter is responsible for controlling compression-driver diaphragm excursion, particularly in the critical region between driver Fs (around 250Hz) and the nominal crossover frequency (anywhere between 700 Hz and 1 kHz, depending on how good the midbass driver is). The task of the lowpass filter is to control out-of-band resonances in the midbass driver and have a smooth phase transfer to the acoustical highpass function. (I usually design the highpass first, since it has the more important job of excursion control, and then design the lowpass to match the required highpass.)
I try to avoid using drivers in the breakup region - I just haven't had very good luck trying to smooth them out electrically (they end up measuring OK, but don't sound right). I've over-equalized speakers in the past, and want to avoid it this time.
It's not entirely a coincidence that the important compression-driver patents (Wente, et al) date back to the days of optical sound-film, with its 8 kHz bandwidth limitation. It wasn't until Dolby and THX started requiring flat response to 15 kHz and beyond that JBL and Altec were forced to re-visit the compromises of the 1945 technology of the Altec 288 and JBL 375.
One of the unusual things about the 7~10 kHz region is that narrow notches in the response are not very audible. Normally, a crossover with the drivers several wavelengths apart is a bad idea due to severe lobing in the plane of drivers. It certainly is tedious to measure, since microphone movements of a few inches cause ripples in the response. I've done supertweeters before, and this particular kind of multi-wavelength crossover is as close to inaudible as any crossover can be. (I still expect some weirdnesses due to the horizontally-wide but vertically-narrow dispersion of the ribbons and what the AH-340 or AH-550 looks like at 7 kHz (2" wavelength). I also expect the 35mm throat size will begin to dominate the pattern of either horn - another reason to cross over to a direct-radiator.)
That is very different from crossovers in the 300 Hz to 5 kHz region, where any errors are immediately audible as a lack of integration and weird position-dependent colorations. Even the famous Lowther is afflicted with a mechanical crossover in the 3~5 kHz region, and this transition to the whizzer-cone is plenty audible and measurable. Crossovers at lower frequencies tend to merge with room colorations due to the very long wavelengths (in practical terms, they can cause unpredictable room colorations that aren't obvious from near-field measurements).
In this design, the really critical crossover is the transition between the 12" direct-radiators and the horn driver. The highpass filter is responsible for controlling compression-driver diaphragm excursion, particularly in the critical region between driver Fs (around 250Hz) and the nominal crossover frequency (anywhere between 700 Hz and 1 kHz, depending on how good the midbass driver is). The task of the lowpass filter is to control out-of-band resonances in the midbass driver and have a smooth phase transfer to the acoustical highpass function. (I usually design the highpass first, since it has the more important job of excursion control, and then design the lowpass to match the required highpass.)
I try to avoid using drivers in the breakup region - I just haven't had very good luck trying to smooth them out electrically (they end up measuring OK, but don't sound right). I've over-equalized speakers in the past, and want to avoid it this time.
It seems lots of challenges coming along the mid horn at both ends of its range to well-integrate with hi and lo ...
So, why not drop the horn and take some direct radiators. There are some good 6~10incher pro mids I guess.
Or, I think this has been discussed, hasn't it? Sorry I'm lost in such a long thread and I forget why they are given up.
So, why not drop the horn and take some direct radiators. There are some good 6~10incher pro mids I guess.
Or, I think this has been discussed, hasn't it? Sorry I'm lost in such a long thread and I forget why they are given up.
Oh, I have some high-efficiency mids as well - a quartet of 18Sound 6ND410's, which look similar to the Audax PR170's mentioned elsewhere in the forum. They will get compared to the horn & compression driver setup, and I suspect the difference between the two will come down to a set of subjective tradeoffs.
The challenge of integrating ANYTHING with the RAAL tweeters is matching the subjective transparency and dynamics. They make most direct-radiator dynamics sound "slow" and low-resolution in comparison - for example, at the RMAF show last autumn, they made the Alnico Lowthers (in an open baffle) sound a bit slow in comparison. Say what you want about Lowthers, in most applications, "slow" is not the word that comes to mind, with the signature ultralight cone and extremely high BL product. (By "slow" I mean subjectively less transparent and open, not anything to do with transient response or HF extension.)
This was the same problem when I heard the Hill Plasmatronics at the 1979 CES in Las Vegas - the Dr. Hill (from Los Alamos) helium-plasma tweeter was extraordinary, truly in class of its own, but it made the rest of the system sound very slow, plodding, and turgid. The Lowther/RAAL combo wasn't as out-of-balance as that, but the mismatch was there.
This is why I'm looking very seriously at large-format compression drivers, with all of their complexities and the endless labyrinth of horn-design arcana. The horn domain makes the medieval Kabbala, or Jungian depth psychology, look simple.
The challenge of integrating ANYTHING with the RAAL tweeters is matching the subjective transparency and dynamics. They make most direct-radiator dynamics sound "slow" and low-resolution in comparison - for example, at the RMAF show last autumn, they made the Alnico Lowthers (in an open baffle) sound a bit slow in comparison. Say what you want about Lowthers, in most applications, "slow" is not the word that comes to mind, with the signature ultralight cone and extremely high BL product. (By "slow" I mean subjectively less transparent and open, not anything to do with transient response or HF extension.)
This was the same problem when I heard the Hill Plasmatronics at the 1979 CES in Las Vegas - the Dr. Hill (from Los Alamos) helium-plasma tweeter was extraordinary, truly in class of its own, but it made the rest of the system sound very slow, plodding, and turgid. The Lowther/RAAL combo wasn't as out-of-balance as that, but the mismatch was there.
This is why I'm looking very seriously at large-format compression drivers, with all of their complexities and the endless labyrinth of horn-design arcana. The horn domain makes the medieval Kabbala, or Jungian depth psychology, look simple.
Oh, I see. The real "PROBLEM" is that almighty RAAL
Talking about large format compression drivers, anyone comes up with the idea of removing the back cap (back chamber)? Just take that big dome as, may be a direct radiator. Or mate it with some wave guide...
This should avoid some of those nasty things with "compression" and phase plugs.
I've heard someone doing this but never listened to one.
An externally hosted image should be here but it was not working when we last tested it.
Talking about large format compression drivers, anyone comes up with the idea of removing the back cap (back chamber)? Just take that big dome as, may be a direct radiator. Or mate it with some wave guide...
This should avoid some of those nasty things with "compression" and phase plugs.
I've heard someone doing this but never listened to one.
Hello Magnetar,
There 2 different schemes:
1) using a Le Cléac'h horn having frequency cut-off lower than 250Hz like the Azura 160Hz and the Azura 204Hz
2) using a Le Cléac'h horn having a cut-off above 250Hz like the Azura 340Hz or the Azura 550Hz.
Some people (like me) are sensitive to phase distortion, but even for those ones phase distortion is nearly no audible below a frequency around 250Hz.
In that case using a Le Cléac'h horn like the Azura 160Hz or 204Hz, even without any high pass crossover is fine (in the range of permissible diaphragm displacement).
But when you use a Le Cléac'h horn having an acoustic cut-off above 250Hz, better to use an high pass crossover one octave or more above its cut-off.
For my own use I derive from pulse mesurement the group delay curve of every horn I use and choose the high pass filter frequency in order than the max equivalent distance to the group delay is less than 10centimeters that means 1/3 foot. This ensure to keep the coherence between the phase of the harmonics and the fundamental.
About directivity, this will be an endless source of dicussions. I meet 3 kind of persons having very different listening habits:
- 1) egotist persons like me (I mean from the point of view of listening to music ) who listen alone in a fixed configuration (armchair, disposition of the listening room ...)
- 2) persons who use to listen in a group (family, friends...) in a fixed central zone of the listening room...
- 3) persons who want to listen from different part of their listening room or even in the neighbouring rooms, even wlking in the room...
For the persons belonging to group 1 the Le Cléac'h horn will ensure pin point 3D imaging, correct tonal balance, very large dynamic due to excellent pulse response. This kind of listening will be the most accurate, like with the best headphones, without the trouble to use headphones.
For the persons belonging to group 2, I know families using with great pleasure such a system
http://www.homecinema-fr.com/forum/album_pic.php?pic_id=798
but, for sure, in that case the persons not sitted at the same distance from the 2 loudspeakers will not benefit from the pin point 3D image mentionned previously...
For people who want to walk in their room while listening to music , PLEASE, simply dont use the Le Cléac'h horn...
Best regards from Paris, France
Jean-Michel Le Cléac'h
There 2 different schemes:
1) using a Le Cléac'h horn having frequency cut-off lower than 250Hz like the Azura 160Hz and the Azura 204Hz
2) using a Le Cléac'h horn having a cut-off above 250Hz like the Azura 340Hz or the Azura 550Hz.
Some people (like me) are sensitive to phase distortion, but even for those ones phase distortion is nearly no audible below a frequency around 250Hz.
In that case using a Le Cléac'h horn like the Azura 160Hz or 204Hz, even without any high pass crossover is fine (in the range of permissible diaphragm displacement).
But when you use a Le Cléac'h horn having an acoustic cut-off above 250Hz, better to use an high pass crossover one octave or more above its cut-off.
For my own use I derive from pulse mesurement the group delay curve of every horn I use and choose the high pass filter frequency in order than the max equivalent distance to the group delay is less than 10centimeters that means 1/3 foot. This ensure to keep the coherence between the phase of the harmonics and the fundamental.
About directivity, this will be an endless source of dicussions. I meet 3 kind of persons having very different listening habits:
- 1) egotist persons like me (I mean from the point of view of listening to music ) who listen alone in a fixed configuration (armchair, disposition of the listening room ...)
- 2) persons who use to listen in a group (family, friends...) in a fixed central zone of the listening room...
- 3) persons who want to listen from different part of their listening room or even in the neighbouring rooms, even wlking in the room...
For the persons belonging to group 1 the Le Cléac'h horn will ensure pin point 3D imaging, correct tonal balance, very large dynamic due to excellent pulse response. This kind of listening will be the most accurate, like with the best headphones, without the trouble to use headphones.
For the persons belonging to group 2, I know families using with great pleasure such a system
http://www.homecinema-fr.com/forum/album_pic.php?pic_id=798
but, for sure, in that case the persons not sitted at the same distance from the 2 loudspeakers will not benefit from the pin point 3D image mentionned previously...
For people who want to walk in their room while listening to music , PLEASE, simply dont use the Le Cléac'h horn...
Best regards from Paris, France
Jean-Michel Le Cléac'h
Magnetar said:
Lynn Olson said:
I need to post some measurements of the little Emilar EK175 driver in a 80 degree conical horn. These measure and sound great. The throat is real short with the EK175, the flare is high and these are the three slit phase plug model (There is another EK175 with 2 slit that is really inferior) - they are quite a bit better then the B&C DE10 if you ignore the response above 15K. Very nice little treble driver horn combination. Maybe this weekend I'll post measurements if I get the time, I am installing two BIG horn subs at friend's to mate with his Rock Monitors- it might get hairy - What's nice about these treble system is above 3K no eq is really needed and they maintain 106 db sensitivity to 'keep up' with a compression mid and match well at the 3K crossover in dispersion- all the mid needs is a hair of eq above 700 (shelf filter) to make it usable to 500 cycles at the same sensitivity as the EK175. This allows for nice integration with a single amp 500 cycles up.
The throat size does NOT tell the whole story of radiation! You will hear/ measure this when you get them setup. The larger horn (I thought it was a lower flare rate then it is because I ignored the extra size needed for the mouth exit, these are a lot bigger than a tractrix for a given flare because of that) may not beam too bad, it actually should be similar to my 350 Hz tractrix horns (half the diameter!) in both low frequency loading and high frequency beaming. It should be fine in the 700 to 1000 crossover region and OK in beaming to 2-3K - The smaller horn may not load well down there though and would be better on top. A catch 22 - I look forward to see how you get this aligned with the ribbon.
Jmmlc said:
Hello,
Well I'm in group 2 for different reasons--------
Beaming sounds unnatural to me, If I want to listen to headphones I 'll listen to headphones! I have 180 Hz Sierra Brooks horns, they are big headphones. The smaller horn is much more acceptable to me and I feel the image is just as 3D - especially with the big dipole bass system. I also feel an additional smaller treble horn eliminates this headphone effect that is still present in the smaller horns if used all the way up.Treble driver horn combination
Hello Magnetar,
What you posted concerning the Emilar EK175 is very interesting. I myself use a 15" + 6.5" + tweeter open baffle speaker, and I am interested in a good treble driver crossed at between 4000-5000 hz with a directivity of round about 60 degrees.
I believe the Emilars are no longer i production, but if you could point me in the direction of a compression driver suitable for the 4-15 kHz+ range and a horn to match I would be gratefull.
I have posted on the subject here (just scroll to the last post):
http://www.diyaudio.com/forums/showthread.php?s=&threadid=120488
Best
Kris
Magnetar said:
Hello Magnetar,
What you posted concerning the Emilar EK175 is very interesting. I myself use a 15" + 6.5" + tweeter open baffle speaker, and I am interested in a good treble driver crossed at between 4000-5000 hz with a directivity of round about 60 degrees.
I believe the Emilars are no longer i production, but if you could point me in the direction of a compression driver suitable for the 4-15 kHz+ range and a horn to match I would be gratefull.
I have posted on the subject here (just scroll to the last post):
http://www.diyaudio.com/forums/showthread.php?s=&threadid=120488
Best
Kris
Hello Lynn,
The expansion of the wavefront area for a Le Cléac'h horn follows the general formula for the hyperbolic horns.
See formula (11) in Bjorn Kolbrek' excellent paper "Horn theory" published by AudioXpress:
http://www.audioxpress.com/magsdirx/ax/addenda/media/kolbrek2884.pdf
For the DIYer the T value can be chosen from 0 to a value over 1.
T = 1 is for an exponential expansion of the area of the curved wavefront. With most high efficiency drivers this results in a slightly upwarding slope of the frequency response curve.
For T =0 you'll obtain a horn with a catenoidal expansion of the area of the wavefront. It is rarely used (but simulations of Le Cléac'h horn with T = 0 shows very few reactance above the acoustical cut-off (but a narrow and tall peak of reactance at acoustical cut-off frequency)
Martin Seddon's Azura horns generally use T from 0.7 to 0.8. This gives a very flat frequency curve on axis. Give a look to the measurements:
http://www.azurahorn.com/Yamaha_on_204.pdf
http://www.azurahorn.com/Yamaha_on_204.pdf
Values of T lesser than 0.7 may be interesting with a driver having (when loaded) a resonance frequency near the acoustical cut-off of the horn.
Low T value also results in longer horns.
Large T values over 1 lead to profile having similarities with conical horns.
Estimation of the acoustical cut-off frequency of a horn from the perimeter length of the mouth is IMHO useless for quasi-infinite horns like the Le Cléac'h horn (or with the Kugelwellen if mouth opened at more than 360°). I call quasi-infinite horns, horns whose mouth shape is able to reduce drastically the reflection of waves (and diffraction at the edges of the mouth).
Measurements shows that if a Le Cléac'h horn profile is calculated with a full mouth curvature (360°) then its cut-off frequency is exactly what was introduced in the calculation (by my spreadsheet or by HornResp ).
The crossover solutions I studied are not devoted to the Le Cléac'h horn specifically. My goal was to obtain low phase distortion and very constant "in coincidence response curve" (this differs of the "power response curve".
Best regards from Paris, France
Jean-Michel Le Cléac'h
The expansion of the wavefront area for a Le Cléac'h horn follows the general formula for the hyperbolic horns.
See formula (11) in Bjorn Kolbrek' excellent paper "Horn theory" published by AudioXpress:
http://www.audioxpress.com/magsdirx/ax/addenda/media/kolbrek2884.pdf
For the DIYer the T value can be chosen from 0 to a value over 1.
T = 1 is for an exponential expansion of the area of the curved wavefront. With most high efficiency drivers this results in a slightly upwarding slope of the frequency response curve.
For T =0 you'll obtain a horn with a catenoidal expansion of the area of the wavefront. It is rarely used (but simulations of Le Cléac'h horn with T = 0 shows very few reactance above the acoustical cut-off (but a narrow and tall peak of reactance at acoustical cut-off frequency)
Martin Seddon's Azura horns generally use T from 0.7 to 0.8. This gives a very flat frequency curve on axis. Give a look to the measurements:
http://www.azurahorn.com/Yamaha_on_204.pdf
http://www.azurahorn.com/Yamaha_on_204.pdf
Values of T lesser than 0.7 may be interesting with a driver having (when loaded) a resonance frequency near the acoustical cut-off of the horn.
Low T value also results in longer horns.
Large T values over 1 lead to profile having similarities with conical horns.
Estimation of the acoustical cut-off frequency of a horn from the perimeter length of the mouth is IMHO useless for quasi-infinite horns like the Le Cléac'h horn (or with the Kugelwellen if mouth opened at more than 360°). I call quasi-infinite horns, horns whose mouth shape is able to reduce drastically the reflection of waves (and diffraction at the edges of the mouth).
Measurements shows that if a Le Cléac'h horn profile is calculated with a full mouth curvature (360°) then its cut-off frequency is exactly what was introduced in the calculation (by my spreadsheet or by HornResp ).
The crossover solutions I studied are not devoted to the Le Cléac'h horn specifically. My goal was to obtain low phase distortion and very constant "in coincidence response curve" (this differs of the "power response curve".
Best regards from Paris, France
Jean-Michel Le Cléac'h
Lynn Olson said:
Lynn
Thanks for the response. I'll show you some measurements and maybe we can work from there?
++++++++++++
>Beaming sounds unnatural to me<
I am aware of beaming, I have a 15" wideband driver that is run fullrange. I know, scary. Now what exactly sounds unnatural to you with regards to beaming?
Thanks
Thanks for the response. I'll show you some measurements and maybe we can work from there?
++++++++++++
>Beaming sounds unnatural to me<
I am aware of beaming, I have a 15" wideband driver that is run fullrange. I know, scary. Now what exactly sounds unnatural to you with regards to beaming?
Thanks
Anglo said:
The easiest way is to put on some music and move your head around. If the sound changes a lot then the speaker is beaming. Panel speakers and big non-CD horns are the worst for this in my experiance. It really screws up the 'power response' too, very unnatural and fatiguing to me. Seems some people live with it though. Big headphones unless you move
Thanks all, much appreciated real-world experience and info. Anglo, the only measurements I can get much use from are FFT's with at least a 5 mSec window, floor reflection removed through acoustical means, and NO SMOOTHING for the computed frequency response. I appreciate seeing the time data with the selected time window (5 to 8 mSec is useful), and the associated FR data that is calculated from the time data. (This is how I present the Ariel data, for example, so the derivation is always clear, along with the choice of window size.)
If the floor reflection is left in the time data, then the CSD is useless, and the FR data is cluttered with comb-filtering that makes fine resolution impossible to read. 1/3 or 1/6 octave smoothing removes the comb-filtering artifacts but also removes evidence of diffraction and narrowband resonances as well. This kind of smoothing dates back the early-Fifties "pen-damping" days at Altec and JBL, and had the very convenient benefit of concealing defects in the horn and compression driver. Now that we no longer use B&K swept-sinewave techniques with a mechanical chart recorder, there's no longer any reason to conceal fine frequency data. (Pixel damping?)
See my measurement article at Nutshell High Fidelity for the kind of data I find useful - pay particular attention to the artifacts generated by comb-filtering from the floor reflections. With spare bits of household items (coats, pillows, blankets, etc.) you can do pretty good job (20 dB) of attenuating the floor bounce, and get much better data as a result.
JMMLC, thanks again for the detailed design criteria for your horns, and the parameters that you've chosen to optimize. I guess I would fall between the Group 1 and 2 listener, although I don't much care for the "giant headphone" effect of some of the biggest horn systems.
The big systems I've heard (with Lowther drivers) had almost no depth reproduction at all, but I could lay that at the door of the Lowthers, with their very uneven wavefront going into the horn thanks to the whizzer driver. A rough, incoherent wavefront at the input end will surely be far worse when it comes out the other end, and that in turn will have severe effects on time-domain and polar-pattern performance.
Conversely, an effective phase-plug, and avoiding diaphragm and surround breakup, should allow the horn to operate closer to what theory indicates should happen. (The validity, or invalidity, of Webster horn theory being a matter for separate discussion.)
I don't think it's fair to blame the horn for defects in driver performance - a horn is not going to magically transform a driver into something it's not. Compression drivers with Mylar diaphragms will sound a lot like Mylar-diaphragm dome tweeters, just many dB louder with more headroom, and the same for all other diaphragm and surround combinations. So front-horn Lowthers still sound like direct-radiator Lowthers, only spatially bigger, louder and with more headroom - and the potential for additional horn coloration.
I no longer believe decades of Altec and JBL propaganda that horns somehow "damp" diaphragm and surround resonance - I see no measured evidence for this claim, and I don't hear it either. The "personality" of the diaphragm, surround, and magnetic-system linearity is always going to be there, impressed on the time, spectral, and distortion domains. I am even more skeptical of claims of "perfect" diaphragm materials with "inaudible" coloration. We've heard that before with titanium, now it's beryllium that's the new wonder material. It measures better, true, but does it sound better?
Marc Henry (of Music Concrete fame) is reporting good results with the 340 Hz horn and the big Radian 950 (2" throat, 4" aluminum diaphragm with Mylar surround) compression driver. JMMLC, are there any other drivers that are personal favorites - old and new?
If the floor reflection is left in the time data, then the CSD is useless, and the FR data is cluttered with comb-filtering that makes fine resolution impossible to read. 1/3 or 1/6 octave smoothing removes the comb-filtering artifacts but also removes evidence of diffraction and narrowband resonances as well. This kind of smoothing dates back the early-Fifties "pen-damping" days at Altec and JBL, and had the very convenient benefit of concealing defects in the horn and compression driver. Now that we no longer use B&K swept-sinewave techniques with a mechanical chart recorder, there's no longer any reason to conceal fine frequency data. (Pixel damping?)
See my measurement article at Nutshell High Fidelity for the kind of data I find useful - pay particular attention to the artifacts generated by comb-filtering from the floor reflections. With spare bits of household items (coats, pillows, blankets, etc.) you can do pretty good job (20 dB) of attenuating the floor bounce, and get much better data as a result.
JMMLC, thanks again for the detailed design criteria for your horns, and the parameters that you've chosen to optimize. I guess I would fall between the Group 1 and 2 listener, although I don't much care for the "giant headphone" effect of some of the biggest horn systems.
The big systems I've heard (with Lowther drivers) had almost no depth reproduction at all, but I could lay that at the door of the Lowthers, with their very uneven wavefront going into the horn thanks to the whizzer driver. A rough, incoherent wavefront at the input end will surely be far worse when it comes out the other end, and that in turn will have severe effects on time-domain and polar-pattern performance.
Conversely, an effective phase-plug, and avoiding diaphragm and surround breakup, should allow the horn to operate closer to what theory indicates should happen. (The validity, or invalidity, of Webster horn theory being a matter for separate discussion.)
I don't think it's fair to blame the horn for defects in driver performance - a horn is not going to magically transform a driver into something it's not. Compression drivers with Mylar diaphragms will sound a lot like Mylar-diaphragm dome tweeters, just many dB louder with more headroom, and the same for all other diaphragm and surround combinations. So front-horn Lowthers still sound like direct-radiator Lowthers, only spatially bigger, louder and with more headroom - and the potential for additional horn coloration.
I no longer believe decades of Altec and JBL propaganda that horns somehow "damp" diaphragm and surround resonance - I see no measured evidence for this claim, and I don't hear it either. The "personality" of the diaphragm, surround, and magnetic-system linearity is always going to be there, impressed on the time, spectral, and distortion domains. I am even more skeptical of claims of "perfect" diaphragm materials with "inaudible" coloration. We've heard that before with titanium, now it's beryllium that's the new wonder material. It measures better, true, but does it sound better?
Marc Henry (of Music Concrete fame) is reporting good results with the 340 Hz horn and the big Radian 950 (2" throat, 4" aluminum diaphragm with Mylar surround) compression driver. JMMLC, are there any other drivers that are personal favorites - old and new?
Lynn,
May be that's the legend of the picture:
http://www.homecinema-fr.com/forum/album_pic.php?pic_id=798
that lead you to speak about Lowther.
In fact, the legend of the picture is erroneous and the system on the picture don't use a single Lowther driver. This system was demoed by Marco Henry at the last Hifi show in Paris few weeks ago and the drivers are 2 x 46centimeters PHL on open baffle (in the corner of the room) to reproduce the lowest frequencies. 2 x Altec 515 in small front horns for bass, one Radian 950 (from memory) on the large circular 200Hz horn and then a small BMS compression driver on 500Hz horn for the high mid + treble.
It was the best sound of the show.
About 2" drivers, a friend of mine use a JBL2441 but with a Radian diaphragm and I could listen his system and appreciated it a lot (far better than with the original JBL diaphragm).
Best regards from Paris, France
Jean-Michel Le Cléac'h
May be that's the legend of the picture:
http://www.homecinema-fr.com/forum/album_pic.php?pic_id=798
that lead you to speak about Lowther.
In fact, the legend of the picture is erroneous and the system on the picture don't use a single Lowther driver. This system was demoed by Marco Henry at the last Hifi show in Paris few weeks ago and the drivers are 2 x 46centimeters PHL on open baffle (in the corner of the room) to reproduce the lowest frequencies. 2 x Altec 515 in small front horns for bass, one Radian 950 (from memory) on the large circular 200Hz horn and then a small BMS compression driver on 500Hz horn for the high mid + treble.
It was the best sound of the show.
About 2" drivers, a friend of mine use a JBL2441 but with a Radian diaphragm and I could listen his system and appreciated it a lot (far better than with the original JBL diaphragm).
Best regards from Paris, France
Jean-Michel Le Cléac'h
Lynn Olson said:
Hi
Thanks Josh and Magnetar for your response. I do know what beaming is, it is the unnatural part that got me intrigued. Of course when sitting in the "sweetspot" the sound is fine and yes once you move out of that spot, well--- it is a different story! I understand what you mean by unnatural when it is explained this way. Again, thanks and yes I agree.
The thing is the slam and weight that the big (see here 15") wideband driver gives makes any other " less beaming" driver (see here smaller) seem obviously smaller. Instruments lose weight and they sound empty, somewhat filled with helium air at times and tone also lacks density.
Those aspects bother me, but again if I could tame the beaming I would probably be "happier". Any suggestions for this would welcomed.
Is there anywhere in this thread where the beaming of a big driver used as a wideband covering the most critical part of the sound i.e 200hz to 4Khz has been talked about?
++++++
Lynn, o.k. thanks. I will do such measurements and address the floor bounce. Looking forward to addressing some issues.
Thanks,
Thanks Josh and Magnetar for your response. I do know what beaming is, it is the unnatural part that got me intrigued. Of course when sitting in the "sweetspot" the sound is fine and yes once you move out of that spot, well--- it is a different story! I understand what you mean by unnatural when it is explained this way. Again, thanks and yes I agree.
The thing is the slam and weight that the big (see here 15") wideband driver gives makes any other " less beaming" driver (see here smaller) seem obviously smaller. Instruments lose weight and they sound empty, somewhat filled with helium air at times and tone also lacks density.
Those aspects bother me, but again if I could tame the beaming I would probably be "happier". Any suggestions for this would welcomed.
Is there anywhere in this thread where the beaming of a big driver used as a wideband covering the most critical part of the sound i.e 200hz to 4Khz has been talked about?
++++++
Lynn, o.k. thanks. I will do such measurements and address the floor bounce. Looking forward to addressing some issues.
Thanks,
"Is there anywhere in this thread where the beaming of a big driver used as a wideband covering the most critical part of the sound i.e 200hz to 4Khz has been talked about?"
I will post a LEAP plot for you of a 15 on an IB board. There is quite a bit of beaming going once you get above 1K. You also use this old nomgraph. I like the LEAP plots better.
Rob
I will post a LEAP plot for you of a 15 on an IB board. There is quite a bit of beaming going once you get above 1K. You also use this old nomgraph. I like the LEAP plots better.
Rob
